Bituminous emulsions



FIP83U4 XR 290611076 ratenred Nov. ii, [936 UNITED (STATES PATENT @FFEQE BITUMINOUS EMULSIONS Lester Kirschbraun, New York, N. Y., assignor to The Patent and Licensing Corporation, New York, N. Y., a corporation of Massachusetts No Drawing. Original application May 26, 1928,

Serial No. 280,964.

Divided and this application February 19, 1934, Serial No. 711,989

2 Claims.

the production thereof being achieved by numerous methods more or less distinct, and with the aid of various types of emulsifying agents. De-

pending upon the emulsifying media employed,

the process by which the emulsification is carried on, and certain other factors, the resultant emulsion products possess certain properties in common, and other properties which are quite marked and'sufiiciently distinctive to enable one skilled in the art to readily distinguish the one type from the other.

Among the latter properties which may to a certain extent be resorted to as a guide in classifying these emulsion products, is the stability of the emulsion under certain definite influences. Thus, certain emulsions begin to set or break, that is, the dispersed particles begin to coalesce with one another, very shortly after the emulsion is exposed to the air, the coalescence of the particles proceeding even in the presence of a considerable proportion of the water content of the emulsion. In other words, in this general class of emulsion, dehydration follows coalescence. The coalescence or breaking of the emulsion under these conditions proceeds of course from those portions thereof that are in more active contact with air, or exposed thereto. Thus, when an emulsion of this type is spread as a layer of considerable thickness, the foregoing action results in the formation of-, a;*skin or scum on the exposed surface of the layer and a more or less sealingin by thisscum or skin of the portions of the layer not in direct contact with air. Accordingly, while certain portions of a layer of emulsion of this type may be readily broken, yet other portions thereof remain unbroken. Apparently there is a more or-less segregation of the phases, with expulsion of water by the breaking action.

Emulsions of this class that are thus readily susceptible to being broken on exposure to air, are in general, relatively unstable and when subjected to certain influences, as for example when spread with a brush, or by the action of electrolytes, or when mixed with finely divided powders or with mineral aggregate, break down immediately.

To the foregoing general type belong emulsions that are produced by the aid of emulsifying agents such as soaps and sulphonated oils. In producing such soap emulsion, the bituminous material,

of whatever character it may be, may be mixed with a suitable quantity of the soap in a water suspension. If desired, the soap may be formed in situ during the process, by first mixingthe bitumen with a saponifiable material, preferably a higher fatty acid 'of the saturated series, such as oleic acid, and thereafter adding to the mixture sufficient quantities of alkali to saponify the fatty acid and form therewith the requisite amount of soap to emulsify the bitumen. This latter procedure is particularly advantageous for the emulsification of the harder varieties of bitumen inasmuch as the saponifiable substance may be selected so as to flux with the base and reduce the hardness of the latter in order to facilitate the emulsification thereof.

Still another class of emulsions thatfall within 'the'general group of relatively unstable emul sions, as already noted, are those made with substances such as sodium silicate as the emulsifying media.

Now, as opposed to this general type of relatively unstable emulsions, there stands another type, the members of which are relatively stable under influences which readily break emulsions of the first group, and as a matter of fact, certain emulsions belonging to this class are easily recognized by their extreme stability. In this class of emulsions, coalescence follows dehydration, the coalescence of emulsions of this type being dependent upon substantially complete removal of the water phase thereof, by evaporation, and such emulsions are not broken or coalesced to any extent upon mere contact with the air. The water phase evaporates uniformly from all portions of a layer of such emulsion, no skin or scum being formed on the surface thereof as is generally the case with emulsions of the unstable type. Hence, these so-called stable emulsions are char acterized by a delayed initial set but the setting when it does occur is uniform throughout the eral p a euem s nsin rgq djyd hjjblays or other analogous finely divided or colloidal mineral powdrsi' ff""'""' Other'emulsions that may be said to' belong to this type are those that are made with gelatin as the emulsifying agent. Emulsions in which starch combined with say 2 to 10% by weight thereof of tannic acid or its equivalent in tannin extract, is used as the emulsifying media, generally possess a sufficient degree of stability to be also grouped in this class.

In the specification and claims the term unstable emulsion is intended to have reference to emulsions of the first class above referred to, namely, those wherein dehydration follows coalescence, while the term stable emulsion is intended to apply to the second class described,

gti tiiii fiosfilows.

air

namely, those emulsions wherein coalescence follows dehydration.

In the commercial application of these bituminous compositions it is found that while the ability of the emulsions of. the first class to set rapidly is advantageous for certain uses, still the general instability of such emulsions, in the pres ence of electrolytes, mineral aggregate, or the like, renders such emulsion objectionable for such use, from this standpoint. On the other hand, if any attempt is made to substitute under such conditions of use, an emulsion of the second general class above mentioned, it is found that while the difiiculties attendant upon the admixture of the emulsion with finely divided powders, mineral aggregate, electrolytes, etc., are largely overcome, yet the necessity for substantially complete removal of. water from such emulsion before it will set, introduces the compensating disadvantages of delayed setting. Thus, for road building purposes, where large quantities of emulsion are used in accordance with well established practice, it is essential that the road material be capable of binding rapidly in damp or cold weather or whenever drying conditions are unfavorable. Soap emulsions, for example, furnish the requirement of rapid initial set, as already pointed out, but the relatively instability thereof, makes it exceedingly difiicult to properly mix certain types of mineral aggregate with the soap emulsion, (and as a matter of fact, special precautions are generally adopted in order to avoid, so far as possible, the breaking down of the emulsionwhile it is being mixed with any aggregate and before the latter is applied to the road foundation). On the other hand, emulsions of the type of which clay emulsions are representative, while sufiiciently stable to permit admixture thereof with mineral aggregate, are objectionable for this use because of the delay incident to the initial setting thereof.

In accordance with my present invention, I arrive at optimum conditions by combining an emulsion of a generally stable character, with one which is relatively unstable, to produce a compound system of an intermediate degree of stability which may be more or less predetermined, depending upon the relative quantities of the separate emulsions thus combined.

The invention may be utilized for example, in connection with road work in which case the proportions of the separate emulsions may be regulated to such a point as will provide the system with the requisite degree of stability to enable the same to be mixed with the desired mineral aggregate and yet sufficient instability to result in a rapid initial set thereof, or at least such an acbeing built. Thus, with sufiiciently rapid skimming over of the emulsion film, the road could withstand action of rain soon after construction.

As a specific illustration of one embodiment of my invention, I may combine an asphalt-clay emulsion with a soap emulsion of. asphalt. The asphalt forming the base of these separate emulsions may be of any desired grade, although preferably asphalt of 100 to 150 F. M. P. may be used. It will also be understood of course, that the invention is applicable also to emulsions of bituminous bases other than asphalt made with similar emulsifying agents.

In some instances, it may be desirable to use a bitumen base of higher melting point to produce the stable clay emulsion than is used in making the soap emulsion. Generally speaking, when using soap or equivalent material as the emulsifying agent, the higher the melting point 5 of the base being dispersed, the more difficult it is to effect dispersion, whereas, on the other hand, when clay or similar material is used in producing a stable emulsion, the emulsification is more diificult to carry out with bases of lower melting point than with those of. relatively high melting point, and the products with harder bitumen are the more stable. The asphalt-soap emulsion may be formed by any of the recognized methods of producing this type of emulsion. In general, the asphalt clay emulsion may be composed of 55-60% asphalt, 40% water, and a small amount of clay. The soap emulsion will ordinarily contain about 70% asphalt, 30% water, and a small amount of soap.

Depending upon the character of the clay emulsion, the alkalinity of the soap emulsion, and other factors, more or less treatment of one of the emulsions may be necessary in order to facilitate the mixing of the two emulsions without causing the relatively unstable soap emulsion to break down during the mixing procedure.- This treatment can best comprise an adjustment of the hydrogen ion concentration, preferably by adding in the specific example cited, alkali to the clay emulsion to bring to a pH value approximating the pH value of the soap emulsion. With the hydrogen ion ..concentrationsof -the separate r 7 emulsions thus adjusted to substantially equal values, the emulsions are rendered more compatible and may then be readily mixed with one another in substantially all proportions.

Thus, an emulsion having a hydrogen ion concentration on the acid side, as for example, a pH of 4.5 to 5.0, may be treated with about 2% by 40 weight thereof of trisodium phosphate to thereby bring it to a pH value of say 8.0 to 8.5, at which point it may be readily mixed in all proportions with the soap emulsion, having a pH value of above 9.0. 1 A

It will be understood that the feature of adjusting the hydrogen ion concentration of the separate emulsions may be resorted to in other instances when mixing a stable emulsion with one relatively unstable, and is not confined necessarily to the procedure wherein a clay emulsion is mixed with a soap emulsion.

It will be understood, however, that in many instances the adjusting treatment may not be necessary at all, since certain emulsions without treatment may be entirely compatible to permit the mixing thereof.

I have heretofore saidthat the separate emu sions, adjusted, if necessary, may be mixed in substantially all proportions. Thus, an asphalt emulsion made with a mixture of several different types of clays as the emulsifying media, and having a pH value of above 6.5, can be mixed in widely varying proportions with an emulsion of asphalt, soap and water.

Where the separate emulsions are combined in about equal parts by weight, the stability of the soap emulsion is enhanced to the point that the compound emulsion may be mixed with electrolytes, finely divided mineral powders, etc., and may be spread with a brush without breaking down. The greater the proportion of stable emulsion in the system, the more stable will the latter be, and conversely, with smaller proportions of the stable emulsion, the compound system is correspondingly less stable and more rapidly undergoes its initial or superficial setting.

That the soap emulsion functions to decrease the time required for the compound system to set can be readily recognized by the appearance of a skin or scum upon the surface of a layer of the mixed emulsion spread upon a plate and left in the open air. This skin or scum resembles closely the skin which forms on the exposed surface of a layer of soap emulsion. The time that elapses before this scum definitely appears is. roughly speaking, a measure of the stability of the system, and the greater the proportion of the unstable soap emulsion present in the system, the

more rapidly does this scum form, thus indicating decreased stability of the system. Whereas, for example, approximately twenty-four hours are generally required for a relatively thick layer of clay emulsion to set, a layer of similar thickness of soap emulsion, which ordinarily begins to set and skin over within about ten minutes after exposure to air, when mixed with the clay emulsion in the proportion of about 50% by weight of soap emulsion on the basis of the clay emulsion, induces an initial setting of the system within a half to three-quartersof an hour, as evidenced by the appearance of the aforesaid skin or scum on the exposed surface thereof. Conversely, of course, the clay emulsion increases the stability of the soap emulsion, the extent of such increase depending upon the relative amount of clay emul- V sion 7 present.

snfin'any'a stable emulsion of asphalt, made with gelatine as the emulsifying agent and containing about asphalt, about 25% water and a small amount of gelatine, may be used to stabilize a soap emulsion of asphalt. The gelatine emulsion and soap emulsion are not miscible in all proportions unless the gelatine emulsion has been treated with a sufiicient amount of alkali to bring it within a compatible range of pH value. The resulting system, with sufficient gelatine emulsion present is stable to substances such as Portland cement, although it is unstable to relatively large quantities of acidic electrolytes.

It will thus be seen that by regulating the proportions of the stable and unstable emulsions, th e stability and time and extent of coalescence of the compound system may be thereby regulated.

A further feature of my invention resides in the production of a compound system characterized as aforesaid, but which, in addition, is of lesser degree of viscosity than either of the emulsions comprising the compound system. It will be appreciated, of course, that while some of these emulsions wherein water constitutes the continuous phase are unstable to dilution, the majority of them} particularly those that are relatively stable, may be thinned to almost any desired extent by dilution with water. However, it is generally desirable to keep the water content of the emulsions as low as possible not only from the standpoint of the additional shipping cost entailed, but also because of the increase in the tendency of the dispersed particles to settle out of suspension upon increased dilution of the emulsion. Hence, in road work. the emulsion must be comparatively thin in order to provide an eiiicient and economic material for coating or penetrating the road metal and yet contain a maximum bitumen content.

I have found, in accordance with my invention, that when a clay emulsion, which, as ordinarily produced, is of comparatively viscid consistency,

is mixed with a soap emulsion of about the same consistency, the resultant compound system when suitably proportioned, is of much thinner consistency than that of either of the component emulsions, and the suspendability of the system is improved, while at the same time the asphalt content is increased relative to the clay emulsion despite the increased fluidity. In fact, with certain types of relatively non-suspendable stable emulsions of the mineral powder type, the resultant system is completely suspendable.

The variations in consistency and fluidity of the mixture may be readily observed, and the proportions at which any desired fluidity can be secured, may be thus predetermined by adding to a given amount of clay emulsion, variable quantitles of the soap emulsion. It will be observed that the initial additions of soap emulsion up to about 30 parts of the soap emulsion to parts clay emulsion, serve to thicken the mixture and beyond this proportion the fluidity of the mixture increases progressively. At about equal parts of the separate emulsions, the mixture becomes very fluid as compared to either of the separate emulsions. A desirable range of fluidity extends from about 40 parts to upwards of 200 parts of soap emulsion to 100 parts of clay emulsion, after which the fluidity of the mixture begins to approach that of the soap emulsion.

A similar phenomenon is observed when mixing gelatin emulsions with soap emulsions, although the critical changes in consistency manifest themselves at somewhat different proportions.

By the use of the terms stable and unstable n? the claims I intend to limit the invention to one wherein the stable emulsion is of a type which is normally miscible in all proportions with an electrolyte, and wherein the unstable emulsion is one which normally is not miscible with all proportions of the same electrolyte.

I claim as my invention:

1. A process of mixing a relatively stable aqueous emulsion comprising bitumen, water and a stable emulsifying agent with a relatively unstable aqueous emulsion comprising bitumen, water and an unstable emulsifying agent which normally would be broken by the relatively stable emulsion which comprises adjusting the hydrogen ion concentration of the relatively stable emulsion to approximately that of the relatively unstable emulsion whereby to render the relatively unstable emulsion compatible for mixing with the relatively stable emulsion, and then mixing the treated relatively stable emulsion with the relatively unstable emulsion.

2. A process of mixing a relatively stable aqueous emulsion comprising bitumen. water and a stable clay-type emulsifying agent with a relatively unstable aqueous emulsion comprising bitumen, water and an unstable soap-type emulsifying agent which normally would be broken by the relatively stable emulsion which comprises adjusting the hydrogen ion concentration of the relatively stable emulsion to approximately that of the relatively unstable emulsion whereby to render the relatively unstable emulsion compatibio for mixing with the relatively stable emulsion, and then mixing the treated relatively stable emulsion with the relatively unstable emulsion.

LESTER KIRSCHBRAUN. 

